Process of soaking ingots



June 4, 1963 R F, DUNN ETAL 3,092,679

PROCESS 0F SOAKING INGOTS Filed March 6, 1962 pit.

3,092,679 PROCESS F SOAKHTG INGTS Robert F. Dunn, Galnnont, and Clarence A. Baeehtel, New Kensington, Pa., assignors to Allegheny Ludlum Steel Corporation, Brackenridge, Pa., a corporation of Pennsylvania Filed Mar. 6, 1962., Ser. No. 177,913 4 Claims. (Cl. 263-52) This invention relates to an improvement in soaking pit practice.

In the operation of steel mills, it is common practice to hold ingots of metal in soaking pits to develop substantially uniform predetermined temperatures therethrough prior to subjecting the ingot to reductions in the blooming mill and the hot rolling mills. The soaking pits are lined with refractory brick and it is common practice to provide a layer of material such as coke breeze, sand or the like over the bottom thereof to protect the brick lining and support the ingot while heating the same.

Where material such as coke breeze (the most commonly used material prior to this invention) is employed, it has been found to be substantially impossible to develop the desired uniform temperature throughout the ingot since the coke breeze does not have suiiicient body and strength to support the weight of the ingot. Instead, the end of the ingot actually sinks into the coke breeze a considerable distance with the result that the enveloping coke breeze about the end of the ingot has an insulating effect to prevent the desired temperature from being developed therein.

Other materials such as sand or the like have proven to be unsatisfactory for use as the beds in soaking pits, especially where high temperatures such as 2300 to .2500 F. are desired in ingots of metal such as stainless steel and silicon iron alloys, since the tine sand forms a. very dense layer. Thus, while the layer of sand willl support the weight of the ingot during heating, it will not absorb the metal liquor that drips from the ingot during the heating thereof at such high temperatures.

Many different materials have been used in the past in attempts to overcome the disadvantages of coke breeze, sand and other materials but to date none of them have proven to be entirely satisfactory for one reason or another. Coke breeze appears to have been the most satisfactory of the known materials for this use but such material has the serious drawback as indicated before of not permitting a uniform temperature to be developed throughout the ingot. Further, coke breeze has a low fusion temperature of about 2400 F. maximum with the result that proper support of the heavy ingots cannot be obtained at the higher soaking temperatures of 2400 to 2500 F.

An object of this invention is to provide an improvement in the soaking-pit practice whereby an adequate support for ingots during the heating thereof and an absorption of liquor drippings therefrom are obtained to thereby permit a uniform heating of ingots in the soaking Another object of this invention is to provide a process of soaking ingots to a substantially uniform predetermined high temperature while supported on a bed formed from anthracite tailings having a predetermined particle size and a predetermined composition which enables the bed to support the ingot while absorbing liquor drippings therefrom.

Other objects of this invention will become apparent from the following description when taken in conjunction with the accompanying drawing, the single FIGURE of which is a schematic view in elevation and partly in sec- Patented June 4, 1963 Y tion of a representative soaking pit illustrating the principles of this invention.

Referring to the drawing, this invention is illustrated by reference to a soaking pit shown generally at 10, the soaking pit being formed of an outer metallic shell 12 and an inner lining 14 formed of refractory material. The soaking pit 10 is provided with a centrally disposed drain 16 which extends downwardly through the bottom of the soaking pit 10, a stopper 18 having a head 20 of refractory material being disposed in such drain to normally maintain the drain closed but being removable therefrom to permit draining from the pit it) as will be explained more fully hereinafter. The mechanism for actuating the stopper 1S is not illustrated as such is well known in the industry. The top of the pit 10 is provided with a plurality of charging openings 22 which are normally covered by removable covers 24 during operation. refractory linings 26 and are provided with rings 28 on the upper surface thereof to facilitate the removal of the covers 24 as by means of a crane or the like. As in normal practice the soaking pit 10 is provided with a plurality of burners indicated at 30 in `one or both of the ends thereof for end liring of the pit 1d to develop predetermined temperatures therein. The pit lli is usually of a size for receiving a plurality of ingots 32 therein, such ingots being admitted through the openings 22 in the top of the pit and being disposed to seat on end in the pit.

In accordance with this invention, in order to properly support the ingots 32 in the pit and to provide for absorption of liquor drippings therefrom under the heat developed in such ingots during the soaking period while protecting the refractory brick lining of the bottom of the pit 14), a layer 34 of anthracite tailings is distributed over the bottom of the pit in a substantially uniform thickness of from 12 to 16 inches to provide a bed in the bottom of the pit. The anthracite tailings utilized in this invention are a waste product of the anthracite coal elds and have a predetermined particle size of less than 1%4 inch with from 90 to 95% of the tailings ranging from 1%4 to 1%4 inch in size with the balance lines of less than %4 inch in size. In practice, it is preferred that such tailings be formed substantially from two particle sizes in the range given in definite percentages, such proportions heing 40 to 45% of tailings having a particle size ranging from %4 inch to 1%4 inch and 48 to 53%. ranging from %4 inch to 6434 inch with the balance being lines of less than %4 inch in size. In practice, the proportion of the tailings in the %4 to %4 inch size is essential together with the fines in order to prevent penetration of the bed by the liquor which drips from the metal ingots as will be explained more fully hereinafter. On the other hand, it is necessary to have from 40 to 45% of the tailings of a particle size ranging from %4 inch to 1%4 inch in order to provide adequate voids in the resulting bed for the absorption of such liquor.

The anthracite tailings utilized in this invention preferably have an analysis comprising from 28 to 35 weight percent of fixed carbon and from 55 to 68 weight percent of ash with the balance being all volatiles and moisture. Such tailings have a fusion temperature, that is, a softening temperature, of ash of 2840 F. as compared to the fusion temperature of 2400 F. maximum of the former commonly used material, namely, coke breeze. The anthracite tailings having the particle size specified hereinbefore are of a more coarse size than that of the commonly used coke breeze with the result that the tailings are cleaner to use in that such tailings do not have the inherent dirty, dusty physical structure of the liner coke breeze.

In practice, assuming that a new pit is to be placed in The removable covers 24 are also provided with operation, the burners 30 are tired to initially Warm up the refractory brick lining of the pit and to remove all moisture therefrom, such moisture escaping through the openings 22 therein when the covers a-re not thereon -and through suitable vents (not shown) which are Yprovided adjacent the top of the pit 10, the temperature of thepit being gradually increased until a temperature of about l900 to 2100 F. is reached. A-t this point, anthracite tailings in an amount sucient to p-rovide approximately 1/2 of the desired thickness of the layer 34 are admitted tov the pit through the openings 22 and are raked orV scraped into a substantially uniform layer over the bottom of the pit to a depth of about 6 to 8 inches thick. This layer is permitted to be heated as by means of the burners 3G to drive oli the volatiles therefrom. In practice, the pit temperature is permitted to increase to a temperature of 2300 to 2350 F. which is effective for burning the tailings to leave a residue of Xed carbon and ash.

The remainder of the tailings is then admitted to the pit 10 in an amount sufficient to complete the desired thickness of 12 to 16 inches in the layer 34 and raked or scraped over the bottomof the pit 10 to provide the substantially uniform thickness of the bed of tailings. Usually a small cavity (not shown) is formed in the bed of tailingsV over thedrain 116 to facilitate accumulation and draining of the liquor yfrom the pit 10' as will be referred to hereinafter. Upon completion of the building of the layer 34 to its desired thickness of ll2 to 16 inches, preferably 14 inches, it is found that the temperature of 2300" to 2350 F. is adequate to burn olf the moisture and volatiles from the layer 34 and to actually effect a sintering of the particles thereof to a form which is composed of only fixed carbon and ash, such particles being in effect of a size and shape substantially the size and shape of the initial chargeof the tailings. It is also found that during the raking or scraping of the tailings to form the substantially uniform thickness required for the bed tha-t the ner portion of the tailings migrates towards thev bottom of the layer -34 to form a more dense layer of the particles of fixed carbon and ash adjacent the brick lining of the bottom of the pit 10 to provide protection for such refractory lining. The resulting sintered but substantially independent particles of fixed carbon and ash are free from clinkers and have suicient strength to support the ingots 32 when admitted to the pit. It is to be noted that the larger particle size which forms the major upper part of the layer 34 provides adequate voids to absorb liquor drippings from fthe ingots. Y

After the layer 34 of the desired particles is formed over the bottom of the pit 10 as described hereinbefore the covers 24 are removed and the ingots 32 which weigh Vfrom 6 to l0 tons are admitted through the openings 22.

and are seated on their ends in spaced relation to one another on the supporting layer 34 of the particles resulting from the firing or burning of the anthracitetailings. As admitted to the pit l10 the ingots 32 Vare usually in a warm condition since such ingots are usually admitted to the pit -directly after having been stripped from the ingot mold (not shown). The covers 24 are replaced over the openings 22 and the burners 30 are operated to increase the temperature developed in the pit 10 to developv a predetermined soaking temperature which will permit the ingots 32 to obtain a substantially uniform predeterminedA temperature of from 2350 to 2500 F. depending upon the metal of the ingot 32 and the melting point of such metal. The soaking temperature is so intense that molten metal drips from the sides of the ingots l32 to form molten liquorat the base of the ingots. However, the upper portion of the layer 34 of the burned products of the tailings contains sucient voids that the liquor is absorbed bythe layer 34 and does not form a pool about the base of the ingot 32, which pool would be undesirable because of its insulating effect on the ingot. The liquor V,which drips yfrom the ingots 32 migrates downwardly through the layer 34 but is substantially prevented from penetrating to the refractory brick lining of the pit 10 by fthe layer of finer particles which has been formed adjacent the refractory brick bottom. AIt is to .be noted that the refractory brick bottom of the pit 10 slopes gently toward the drain 16, such slope cooperating with the layer of fired nes of the tailings and the cavity (not shown) in such layer to permit the migration of the liquor towards the drain l. Throughout this soaking operation, it is found that the sintered particles of the tailings have sufficient strength to support the ingots on end Without permitting the ingots to penetrate or sink into the layer 34 more than one to two inches whereby the ingot can be uniformly heated throughout its length.

After ythe desired uniform temperature has been developed in the ingot 32, the cover 24 is .removed and the utilizing the same bed formed of the layer 314 of tailings until -it appears from visual examination that too large a quantity of liquor is .being accumulated in the bottom of the pit to the point where the level of the liquor is approximating the thickness of the layer 34. In some instances, it may be desirable to add a make-up quantity of tailings in zbetween charging of the ingots 32 so as to insure an adequate bed of the sintered particles of the tailings to support the ingots above the layer of liquor which is being accumulated in the bottom of the base of the pit 19. Usually, however, the liquor and sintered particles of the tailings are drained from the bottom of the pit 1t? after no more than two soaking periods as it is desired to maintain a layer 34 of the sintered particles of the tailings which will provide adequate support for the ingots and prevent any substantial penetration of such particles by liquor dripped from theingots to a depth where damage can be done to the refractory bottom lining, of the pit 10.

This invention makes it possible to obtain a more etlicient soaking of ingots while at the same time utilizing a relatively inexpensive waste product from the anthracite coal fields. -A more efficient soaking of the ingots is obtained since the material utilized for the supporting bed has adequate strength to support the ingots without permitting the penetration thereof to any marked degree with the result that a substantially uniform temperature is developed in the ingot from end to end. Further, because of the predetermined size of the particles utilized in forming-the layer 34 `absorption of the liquid dripped vlfrom the ingots is obtained while at the Sametime penetration of the liquor to the refractory brick bottom is substantially prevented. The high fusion temperature of the particles utilized in forming the layer 34 also makes it possible to more eiiciently utilize the higher soakingtemperatures necessary in a number of the present day steel mill practices.

' We claim:

1. In the process of soaking an ingot of metal to a predetermined substantially uniform temperature in a soaking pit lined with refractory material and having a bottom drain therein, the combination comprising, covering the bottom of the pit with a layer of particles of anthracite tailings to a substantially uniform thickness of 12 to-16 inches while heating the pit to a temperature in the range of 1900 to 2350" iF. to warm the refractory lining, said tailings having a predetermined particle size ofless than 1%4 inch with from 90 to 95% of said tailings ranging from %i to 1%4 inch in particle size and the balance iines of less than 1%4 inch in particle size, said tailings having an analysis comprising from 28 to 35 weight percent of fired carbon and from 55 to 68 weight percent of ash and the balance substantially all volatiles and moisture, maintaining the temperature in the pit within said range to remove the volatiles and moisture from the tailings and effect a sintering of the xed carbon and ash of the particles thereof in substantially the initial particle sizes of the tailings, placing the ingot in the pit, seating the ingot on and supporting the ingot by the sintered particles, increasing the temperature of the pit to a predetermined soaking temperature where metal from the surface of the ingot drips downwardly therefrom and forms molten liquor in the pit, the sintered particles functioning to absorb the liquor therebetween while preventing any substantial penetration thereof to the refractory lined bottom of the pit, removing the soaked ingot from the pit, and draining the liquor through the bottom drain of the pit, the liquor carrying the sintered particles from the pit to thereby effectively clean the pit.

2. In the process of soaking an ingot of metal to a predetermined substantially uniform temperature in a soaking pit lined with refractory material and having a bottom drain therein, the combination comprising, covering the bottom of the pit with a layer of anthracite tailings to a substantially uniform thickness of 6 to 8 inches while heating the pit to an initial temperature of l900 to 2100 F. to warm the refractory lining and remove volatiles and moisture from the tailings, increasing the temperature in the pit to within the range of 2300 to 2350 F., adding additional tailings to the initial layer to form a combined layer having a substantially uniform thickness of 12 to 18 inches, said tailings having a predetermined particle size of less than 1%4 inch with from 90 to 95% of said tailings ranging from 3/64 to 1%4 inch in particle size and the balance fines of less than 5%;4 inch in particle size, said tailings having an analysis comprising from 28 to 35 weight percent of xed carbon and from 55 to 68 weight percent of ash and the balance substantially all volatiles and moisture, maintaining the temperature in the pit within said range of 2300 to 2350 F. to remove the volatiles and moisture from the tailings and effect a sintering of the Xed carbon and ash of the particles thereof in substantially the initial particle sizes of the tailinvs, placing the ingot in the pit, seating the ingot on and supporting the ingot by the layer of sintered particles, increasing the temperature of the pit to a predetermined soaking temperature where metal from the surface of the ingot drips downwardly therefrom and forms molten liquor in the pit, the sintered particles functioning to absorb the liquor therebetween while preventing any substantial penetration thereof to the refractory lined bottom of the pit, removing the soaked ingot from the pit, and draining the liquor through the bottom drain of the pit, the liquor carrying the sintered particles from the pit to thereby effectively clean the pit.

3. In the process of soaking an ingot of metal to a predetermined substantially uniform temperature in a soaking pit lined with refractory material and having a bottom drain therein, the combination comprising, admitting anthracite tailings to the bottom of the pit, distributing said tai-lings over the bottom of the pit to form a layer of subsantially uniform thickness of l2 to 16 inches while heating the pit to a temperature in the range of 1900 to 235 0 F. 'to Warm the refractory lining, said tailings having a predetermined particle size of less than 1%4 inch with from 90 to 95% of said tailings ranging from %4 to 1%4 inch in particle size and the balance fines of less than %4 inch in particle size, said tailings having an analysis comprising from 28 to 35 weight percent of xed carbon and from 55 to 68 weight percent of ash and the balance substantially all volatiles and moisture, said distribution of the tailings effecting a migration of the ner particle size towards the bottom of the pit to form a dense layer thereacross and to provide an upper portion of the tailings having voids therein, maintaining the tempetraure in the pit within said range to remove the volatiles and moisture from the tailings and eect a sintering of the Xed carbon and ash of the particles thereof in substantially the initial particle sizes of the tailings, placing the ingot in the pit, seating the ingot on and supporting the ingot by the sintered particles, increasing the temperature of the pit to a predetermined soaking temperature where metal from the surface of the ingot drips downwardly therefrom and forms molten liquor in the pit, the upper portion of the layer of sintered particles functioning to absorb the liquor therebetween while the more dense lower portion of the layer of sintered particles prevents any substantial penetration of the liquor to the refractory lined bottom of the pit, removing the soaked ingot from the pit, and draining the liquor through the bottom drain of the pit, the liquor carrying the sintered particies from the pit to thereby effectively `clean the pit.

4. In the process of soaking an ingot of metal to a predetermined substantially uniform temperature in a soaking pit lined with a refractory material and having a bottom drain therein, the combination comprising, admitting anthracite tailings to the bottom of the pit, distributing said tailings over the bottom of the pit to form a layer of substantially uniform thickness of 6 to 8 inches while heating the pit to an initial temperature of 1900 to 2100 F. to Warm the refractory lining and remove volatiles and moisture from the tailings, increasing the temperature in the pit to within the range of 2300 to 2350o F., adding additional tailings to the initial layer to form a combined layer having la substantially uniform thickness of l2 to 18 inches, sai-d tailings having a predetermined particle size of less than 1%4 inch with from 90 to 95% of said tailings ranging from 64 to 1%4 inch in particle size and the balance fines of less than 3;@4 inch in particle size, said tailings having an analysis comprising from 28 to 35 weight percent of fixed carbon and from 55 to 68 weight percent of ash and the balance substantially all volatiles and moisture, said distribution of the tailings effecting a migration of the finer particle sized tailings towards the bottom of the pit to form a dense protecting layer thereacross and to provide an upper portion of the tailings having voids therein, maintaining the temperature in the pit within said range of 2300 to 2350 F. to remove the volatiles and moisture from the 'tailings and effect a sintering of the fixed carbon and ash of the particles thereof in substantially the initial particle sizes of the tailings, placing the ingot in the pit, seating the ingot on and supporting the ingot by the layer of sintered particles, increasing the temperature of the pit to a predetermined soaking temperature where metal from the surface of the ingot drips downwardly therefrom and forms molten liquor in the pit, the upper portion of the layer of sintered particles functioning to absorb the liquor therebetween While the more dense lower portion of the layer of sintered particles prevents any substantial penetration of the liquor to the refractory lined bottom of the pit, removing the soaked ingot from the pit, and draining the liquor through the bottom drain of the pit, the liquor carrying the sintered particles from the pit to thereby effectively clean the pit.

No references cited. 

1. IN THE PROCESS OF SOAKING AN INGOT OF METAL TO A PREDETERMINED SUBSTANTIALLY UNIFORM TEMPERATURE IN A SOAKING PIT LINED WITH REFRACTORY MATERIAL AND HAVING A BOTTOM DRAIN THEREIN, THE COMBINATION COMPRISING, COVERING THE BOTTOM OF THE PIT WITH A LAYER OF PARTICLES OF ANTHRACITE TAILINGS TO A SUBSTANTIALLY UNIFORM THICKNESS OF 12 TO 16 INCHES WHILE HEATING THE PIT TO A TEMPERATURE IN THE RANGE OF 1900* TO 2350*F. TO WARM THE REFRACTORY LINING, SAID TAILINGS HAVING A PREDETERMINED PARTICLE SIZE OF LESS THAN 12/64 INCH WITH FROM 90 TO 95% OF SAID TAILINGS RANGING FROM 3/64 TO 12/64 INCH IN PARTICLE SIZE AND THE BALANCES FINES OF LESS THAN 3/64 INCH IN PARTICLE SIZE, SAID TAILING HAVING AN ANALYSIS COMPRISING FROM 28 TO 35 WEIGHT PERCENT OF FIXED CARBON AND FROM 55 TO 68 WEIGHT PERCENT OF ASH AND THE BALANCE SUBSTANTIALLY ALL VOLATILES AND MOISTURE, MAINTAINING THE TEMPERATURE IN THE PIT WITHIN SAID RANGE TO REMOVE THE VOLATILES AND MOISTURE FROM THE TAILINGS AND EFFECT A SINTERING OF THE FIXED CARBON AND ASH OF THE PARTICLES THEREOF IN SUBSTANTIALLY THE INITIAL PARTICLE SIZES OF THE TAILINGS, PLACING THE INGOT IN THE PIT, SEATING THE INGOT 